Straight from Microsoft Technet:
"Windows XP Service Pack 3 (SP3) includes all previously released updates for the Windows XP operating system, in addition to a small number of new updates. Windows XP SP3 will not significantly change the Windows XP experience."
The only reason SP1A or SP2 is required when installing from Windows Update is all of the service pack files are not installed throught Windows Update just the ones relevant to your system which is what your link refers to. SP1A ans SP2 add updated installer files required to install SP3 through Windows Update. This is the reason I do not use Windows Update to install Service Packs. Installing SP3 using the full download network install version does not require SP1A or SP2 to be installed. Nor do you need to slipstream them in addition to SP3 since as stated above it is a cumulative update.
Edited by Baltboy, 11 January 2011 - 05:28 PM.
Get your facts first, then you can distort them as you please.